Dielectric antenna array



Dec. 30, 1952 M. cs. BOUIX 2,624,002

DIELECTRIC ANTENNA ARRAY Filed Aug. 18, 1950 2 SI-IEETSSHEET 2 FIG. 4

FIG. 5

A e/m l I /lg= f(0) ,./lg= 5.34 em Aa=2225m 4Q LQ J 4 2 95 1 2.225 f l 1 i 1 R. g a m/m m INVENTOR MAURICE G. BOUIX,

ATTORNEYS Patented Dec. 30, 1952 UNITED STATES ATENT OFFICE DIELECTRIC ANTENNA ARRAY Maurice 'Bouix, Paris, France .ApplicationAugust 18, 1950, Serial No. 180,226" .In France August 19, 1949 :main guide and coupled to it by means of coupling holes. Cylindrical portions of dielectric material of the same height are inserted inside these segments and have characteristics so designed that they vary the phase-velocity of the wavelets travelling through the segments so that these wavelets, whichenter the dielectric portions with differences of phase delay due to the spacing of the segments on the main guide, are in phase with one. another at the points where they leave tine-inserted dielectric portions.

The dielectric portions may be said to act as itransfonmers; for instance they act ashalf-wave transformers if their height is equal to half the wavelength in the guide segments in which they are inserted.

The invention will be better understood from Ithje1followihg detailed description, with reference to. the accompanying drawings in which:

Figure 1 illustrates a first embodiment of a compresise array;

Figure z is a graph showing the relative resist! ance and reactance of a polyrod plotted against theadiameter oi-a coupling hole by which therod is'couplejd to the main guide;

Figure :3 is a graph of the length of the matching screw facing each coupling hole inside the main guide, plotted against the diameter of the coupling hole;

Figure 4.:representsa1sec0nd: em odim n s-f a compressed array; and

Figure 5 :represents a 'curvezgiving the wavelength insa circular guide of. aHntravellingrwave, plotted against the diameter :of the guide.

.Figure .1. refersto a compress d ar ay, .iniW h all the rods: radiate oophasal waveletsgthe-polarisation-of which is paralled to thearray, and this in spite of their being coupled to the rectangular feed :guide at mutual distances less than the guide wavelength Ag; In this example under consideration the" spacing it between the rodsis equal to ,22, 32 are segments of circularguides.

2 i. e. there are three polyrods within two guide wavelengths Ag. The numeral 1 denotes the rectangular feed guide, 6 denotes an ultra high frequency power source, I, ll, 2|. 3| are dielectric rods and 4, I4, 24, .34 are the coupling holes. 5, I5, 25, 35 are the matching screws and 2, l2, 3, I3 23, 33 are the-flanges of said segments vvelded'to the broad side of thegu-ide F.

'In the circular guide 2- fill'ed' with a dielectric substance where the guide wavelength is K and the cut-off wavelength is M, we'have:

wherein-M denotes-the wavelength in freespace, A the wavelength in "the dielectric medium, tthe electric inductive capacity of the medium (='232'- 5 for polythene and denot'es-i-ts'magneti-cinductiye capacity (=1 f or polythene).

The circular guide 1 2 is fed at its basis with a wave which has a phase retardation of due to its propagation over the distance u in the rectangular guide 1, withtrespect to the wave feeding the circular guide 2 at, its basis.

In the circular. guide :lzlan h- :hish ni ra on is introduced .of. a dielectric substance of: inductive capacities 61 and 1 and of guide waveelengthag determined in such a manner that the phase-shift delay introducedhy the portion of the dielectric substance, added to thezphaser-shift delay due to the propagation, would give a total phaseshift of Zr, and that the height of the dielectric substance would act as a half-wave transformer. Then. we shall have:

By substituting to h and to )\g their respective expressions embodied in Equations 1 and 2, we shall have:

Assuming ,u1=,u=1, we shall have:

By choosing a wavelength in free space:

Ao=3.34 cm. i

and a circular guide of a radius of 1.6 cm., and

therefore a cut-off wavelength of \c=1.6 1.7=2.72 cm In the same manner, in the circular guide 22 Ian hhigh portion of a dielectric substance will be introduced having inductive capacities 62 and .-,uz and a guide wavelength I determined in such .,'a manner that the phase-shift delay introduced by this portion of dielectric substance, added to the phase-shift delay due to the propagation, would give a total phase- :shift of 411-, and that the height of the dielectric substance would act as a three-halves wave By substituting to h and to k theirrespective expressions embodied in Equations 1 and 3, we

shall have:

Assuming [L2=',u=1, we shall have:

g a a F 25 A...

Adopting for 7w, 7w, and e the same values as before, we shall have:

mass" In order to obtain a given distribution of power, that is a uniform distribution in which equal electromagnetic energy is delivered to all the radiators, or a gabled distribution in which the energy delivered increases symmetrically from the end radiators of .the array to the middle radiator, the following procedure is adopted:

In an article entitled Slot guides and their application to antennae published in the Annales des Telecommunications, volume 4, No. 3, pages '75 to 86, the applicant has disclosed two tables giving the values of the product GXN, wherein G is the relative conductance of a radiator (i. e. the real part of the relative admittance), and N is the number of radiators; this product is given for two cases, namely for a gabled distribution and for a uniform distribution. When the system comprises a great number of radiators, in order to avoid having a different coupling between each radiator and the main guide, a group of consecutive radiators are coupled to the main guide by like couplings calculated for the first radiator of the group, then a second group of radiators are coupled to the main guide by couplings calculated for the first radiator of the second group, and so on.

For a serial arrangement of the radiators, on the feed guide, like that of the polyrods of Figure 1, it will suffice to replace, in these tables, the value of G by the value of R, which is the relative resistance of the radiators I, I I, 2 I, 3I.

Assuming that the array of Figure 1 comprises 32 radiators grouped in pairs, the table reproduced hereafter gives, for the case of a uniform distribution of power, the relative resistance of each radiator, the radiator denoted in the table by the numeral 1 being the radiator marked I in Figure 1, the radiator denoted by 2 in the table being the radiator marked 'II in Figure 1 and so on.

No. of Group radiator R X N R 1 1 l. 01 0. 0315 2 l. 01 0. 0315 2 3 1. 01 0. 0315 h 4 1. 01 O. 0315 3 5 1. 15 0. 0359 6 1. 15 0, 0359 4 7 1. 15 0. 0359 8 1. 15 U 0359 9 1. 35 0. 0421 1 1. 35 Y O. 0421 11 1. 35 0. 042]. I 12 1. 35 0, 0421 13 1. ,63 0. 0509 14 1. 63 010509 15 1. 63 0. 0509 16 1. 63 0. 0509 17 2. 04 0. 0637 18 2. 04 0. 0637 19 2. 04 0. 0637 20 2. 04 0. 0637 11 21 2.53 0. 0790 22 2. 53 0. 0790 12 23 2. 98 0. 0931 n 24 2. 98 O. 0931 3 25 3. 68 0. 115 26 3. 68 O. 115 14 27 4. 77 0. 149 h 28 4. 77 O. 149 15 29 6. 83 0. 213 30 6. 83 0. 213 16 31 11.87 0. 371 32 11. 87 O. 371

The curve II; of Figure 2 indicates thus' the diameter of the coupling hole of each radiator as depending on the resistance of this latter. In this curve the portions on opposite sides of the line 20 corresponding to the point marked ID are plotted with abscissae in difference scales. The part of the curve on the left hand side of the line 20 has been established according to the formula of Bethe giving the law of variation of the resistance as a sixth power D of the diameter D of the coupling hole, see Bethe, The-;

' 1 cry of diffraction by small holes, Physical'Review, 1944, 66, page 163. The portion of the curve to the right of the line 20 results from measurements carried out by the applicant.

These measurements have been carried out for a wavelength in free space of M=3.34 cm., a

rectangular guide of 22.86 10l6 mm., and polythene dielectric radiators of 16 mm. diameter.

The curve 19 of the same Figure 2 gives the 'reactance of each radiator as plotted against the diameterof the coupling hole.

The curve 29 of Figure 3 gives the depth of advance of the screws 5, I5, 25, 35 (assumed to be of 3 mm. diameter) as plotted against the diradiating rods the requisite diameter of Bethe 'holes may become greater than the broad side of the guide. In this case the narrow side of the rectangular guide I will be reduced, so reducing the characteristic impedance of the guide and thus the power transmitted through the coupling hole will increase.

If it is intended to radiate or receive a wave polarised perpendicularly to the array, i. e. perpendicularly to the longitudinal edges of th rectangular guide, the coupling holes are bored in the narrow side of the rectangular guide, and the segments of circular guides serving as sockets for dielectric rods are connected to this narrow side.

Figures 4 and dare relative to a compressed array in which the diameter of each circular guide 29, 39 serving as socket to each polyrod 28, 38 has been modified in order to modify the phase velocity in this circular guide. In this example the spacing U along the guide 3'! fed by the source 36 between the rods is equal to that is to say there are two polyrods within one wavelength of guide 31.

Let H be the common height of all the circular guide segments, Ng the wavelength in the guide segment 29, and Ng the wavelength in the guide segment 39.

The circular guide 29 causes a certain phaseshift :1: =27! E to the wavelet which it receives at its base input. In the same manner the circular guide 39 causes a phase-shift:

to the wavelet which it receives at its base input, and which is shifted by 1r with respect to the wave received at the base of the preceding guide. The condition that the waves feeding the two polyrods 29 and 39 be cophasal is:

Figure represents the wavelength k in a circular guide as depending on the radius a of this To each value of A of the curve M corresponds a radius a of the circular guide. It will be noted that the Equation 4 comprises a parameter as which may be chosen at will. For practical reasons, in the above example the value has been adopted;

that is to say:

Elsi

If we take =2.93 cm. to which corresponds, on the curve H, a radius of 10 mm. of the circular guide, we shall have =4.10 cm. to which cor responds, on the same curve, a radius of 7.8 mm.

Then a value of 51 mm. will be found for H.

The array of Figure 4 will thus comprise odd polyrods identical to 28 and even polyrods identical to 39, the odd ones having a widened root of 20 mm. of diameter fitted into the circular guide segments 29 having the same diameter and a height of 51 mm, and the even ones having a narrowed root of 15.6 mm. of diameter fitted into the circular guide segments 39 having the same diameter. In order to compensate for the cross-section variations between the portions of the radiators situated outside the guide segments and the portions of the same radiators situated inside of the guide segments, the reactance in each coupling point will be matched by actuating the screws 39, 49

Although the invention has been described with reference to particular examples, its scope appears sufiiciently from the foregoing description to enable a man skilled in the art to apply the same to any dielectric array having a desired distribution of power.

What I claim is:

1. A compressed dielectric antenna array comprising a single rectangular air filled main wave guide, means for introducing ultra high frequency waves into said main wave-guide, circular guide segments of the same height welded to said main guide, coupling and matching means comprising holes bored in one wall of the main guide and located on the axis of said guide segments and matching screws facing the holes located in the opposite wall of the main guide, the spacing of adjacent guide segments being smaller than one main-guide wave length and equal to some simple submultiple of said wave length, whereby a given number group of guide segments is coupled to the main guide along each wave length of said guide, radiating circular dielectric rods filled into said circular segments and the bases of which come into contact with the wall of the main guide in which the holes are bored, cylindrical portions of dielectric material of the same height, all terminating in the same plane, located inside all the guide egments except the first of each group and being a part of the bases of the rods, said dielectric portions being adapted to cause simultaneously such a phase shift delay that the wavelets radiated by all the rods be cophasal and such a wave length in the guide segments in which they are located that the height of the dielectric portions be an integral number of halves of said wave length.

2. A compressed dielectric antenna array comprising a single rectangular air filled main wave guide, means for introducing ultra high frequency waves into said main wave guide, circular guide segments of the same height welded to said main guide, coupling nd matching means comprising holes bored in one wall of the main guide and located on the axis of said guide segments and matching screws facing the holes located in the opposite wall of the main guide, the spacing of adjacent guide segments being smaller than one main guide wave length and equal to some simple su-bmultiple of said wave length, whereby a given number group of guide segments is coupled to the main guide along each wave length of said guide, radiating circular dielectric rods filled into said circular segments and the bases of which come into contact with the wall of the main guide in which the holes are bored, cylindrical portions of dielectric material of the same height, all terminating in the same plane, located inside all the guide segments except the first of each group and being a part of the bases of the rods, said dielectric portions having dielectric constants determined to cause simultaneously such a phase shift delay that the wavelets radiated by all the rods be cophasal and such a wave length in the guide segments in which they are located that the height of the dielectric portions be an integral number of halves of said wave length.

3. A compressed dielectric antenna array comprising a single rectangular air filled main wave guide, means for introducing ultra high frequency waves into said main wave guide, circular guide segments of the same height welded to said main guide, coupling and matching means comprising holes bored in one wall of the main guide filled into said circular segments and the bases of which come into contact with the wall of the main-guide in which the holes are bored, cylindrical portions of dielectric material of the same height, all terminating in the same plane, located inside all the guide segments except the first ofeach group and being a part of the bases of the rods, said dielectric portions being constituted of the same dielectric material as the radiating rods and having diameters determined to cause simultaneously such a phase shift delay that the wavelets radiated by all the rods be 00-- phasal and such a wave length in the guide segments in which they are located that the height of the dielectric portions be an integral number of halves of said wave length.

MAURICE G. BOUIX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,415,242 Hershberger -Feb. 4, 1947 2,453,414 De Vore Nov. 4, 1948 2,534,451 Kahan et al Dec. 19, 1950 

